Sibling aggression is surprisingly common and sexually egalitarian

Amanda P. Kirsch, Douglas T. Kenrick, Ahra Ko, Cari M. Pick, Michael E.W. Varnum

Research output: Contribution to journalArticlepeer-review


Two well-supported generalizations from aggression research are that: a) people are less likely to commit homicide against close kin compared to non-kin, and b) females are less likely to engage in direct aggression than are males. Aggression between siblings, however, is somewhat more complicated than one might surmise from those two generalizations. Data from 3 studies collected using undergraduate and Prolific samples (N = 1640) reveal classic sex differences in direct aggression between non-relatives, but not between sisters and brothers. Whereas only a small minority of females have hit a friend or an acquaintance, the majority of females, like the majority of males, have hit a sibling. Although reputational aggression is substantially less likely between siblings than between friends or acquaintances, mild forms of direct aggression (such as hitting) are quite frequent between siblings. Discussion considers several possible limitations of the findings reported here and considers results in light of Trivers' theory of parent-offspring conflict.

Original languageEnglish (US)
Pages (from-to)214-227
Number of pages14
JournalEvolution and Human Behavior
Issue number2
StatePublished - Mar 2024


  • Familial aggression, sibling rivalry
  • Reputational aggression
  • Sex differences

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Experimental and Cognitive Psychology
  • Arts and Humanities (miscellaneous)


Dive into the research topics of 'Sibling aggression is surprisingly common and sexually egalitarian'. Together they form a unique fingerprint.

Cite this